Module overrides 

Layered option overrides (M.2.1).

Modes (and other layer producers — buffer-local sets, modal-state hooks) contribute typed overrides via OptionOverride. The resolver in lattice-config walks the layers in priority order (mode-architecture.md §6.1) and picks the first non-empty value per option for scalars; collection-shaped options concatenate.

Why this lives in lattice-config

Mode::options() (in lattice-mode) returns an OptionOverrideSet. These types once lived in lattice-mode to break a lattice-mode → lattice-config → lattice-core → lattice-mode cycle; the M.4 dependency inversion removed Document::modes from lattice-core, retiring the cycle, so the layer inputs now sit beside the crate::Resolver and crate::ResolvedOptions they feed. lattice-mode re-exports them.

Type-safe construction via lattice-config’s overrides!

Modes don’t construct OptionOverride directly with the erased OptionOverride::new API. Instead they use the overrides! macro from lattice-config, which has access to OptionDecl and emits compile-time-typed wrappers around OptionOverride::new:

use lattice_config::{OptionOverrideSet, OverridePriority, Tabstop, Wrap};

fn options() -> OptionOverrideSet {
    lattice_config::overrides! {
        Tabstop = 4,
        #[priority(High)]
        Wrap = false,
    }
}

let set = options();
assert_eq!(set.len(), 2);
let wrap = set.iter().nth(1).unwrap();
assert_eq!(wrap.downcast_value::<bool>(), Some(&false));
assert_eq!(wrap.priority, OverridePriority::High);

The macro asserts at compile time that each value matches its declaration’s Value type. Direct OptionOverride::new is reserved for the WIT plugin adapter (M.10), where declarations are runtime data and TypeId is the only handle.

Structs

OptionOverride

One option-value override from a single layer producer (a mode, a buffer-local set, a modal-state hook).

OptionOverrideSet

A set of OptionOverrides contributed by one layer producer (typically the return value of Mode::options()).

Enums

OverridePriority

Tie-break priority for two layer entries that target the same option.